With the development of electronic equipment such as for computers and portable information-processing equipment terminals, the use of liquid crystal display devices, in particular color liquid crystal display devices is increasing. This type of liquid crystal display device uses a color filter in order to color the display image. The color filter has a substrate, and is formed by impacting liquid of R (red), G (green), B (blue) in a predetermined pattern onto the substrate. As such a method of impacting liquid such as ink onto the substrate, a droplet discharge method (ink jet method) is adopted.
In the case where a droplet discharge method is adopted, a predetermined amount of drawing (film producing) liquid is discharged (ejected) from a droplet discharge head and impacted on the film. However this substrate, as disclosed for example in the following patent literature 1, is mounted onto an XY stage (a stage which can move freely in two dimensions along an XY plane). By moving the substrate in the X-direction and the Y-direction by means of this XY stage, liquid from a plurality of droplet discharge heads can be impacted on predetermined positions on the substrate.
Patent Literature 1: Japanese Unexamined Patent Application First Publication No. Hei 8-271724A (FIG. 5)
However, in the abovementioned background art, there are the following problems.
Regarding the liquid discharged from the droplet discharge head, liquid stored in a liquid tank is supplied to the droplet discharge head via a tube or the like to fill the head. However at the time of initial operation, or for example after being suspended for around one day, since the liquid is not filled into the head, it is necessary to introduce the liquid to as far as the droplet discharge head.
Therefore, heretofore, a method is often adopted which involves connecting a negative pressure suction mechanism such as a pump or tube constituting a suction drive source to a cap which covers the liquid discharge face of the droplet discharge head to prevent drying, and applying a negative pressure suction under conditions with the cap abutted against the droplet discharge head, to thereby introduce and fill a liquid from the liquid tank via the tube to the droplet discharge head.
In the case of a liquid of a relatively low viscosity used for a printer or the like, when the liquid is filled into the droplet discharge head, in most cases bubbles existing inside the droplet discharge head can be exhausted. However in the case where a liquid of a high viscosity is filled into the droplet discharge head, the bubbles cannot be completely discharged. If bubbles remain inside the head, a problem arises in that the liquid is not discharged, and even if discharged the speed and weight fluctuates, so that the discharge characteristics for the liquid are not stable. In particular, recently, there is a movement to widely adopt the droplet discharge device, not only for printers, but also for industrial use. Therefore, it has become highly desirable to develop a technique for filling a head so that even with a liquid of a high viscosity there are no residual bubbles.
Moreover, in the case where a high viscosity liquid is used in a droplet discharge head, in addition to the above mentioned problem of initial filling, there is a problem in that the nozzle apertures clog due to a thickening of the liquid during pausing of the discharge head.